[Bug runtime/3916] improve timing monotony

[joshua dot i dot stone at intel dot com]

------- Additional Comments From joshua dot i dot stone at intel dot com  2007-01-24 18:52 -------
If I may link to the relevant threads...

The first report was here:
http://sourceware.org/ml/systemtap/2007-q1/msg00174.html

My reply tries to explain *why* the current implementation has this deficiency:
http://sourceware.org/ml/systemtap/2007-q1/msg00175.html

These further replies seem to confirm my hunch that the resync with kernel time
is causing the negative intervals, as the resync happens in a timer callback
(i.e. during softirq-timer).
http://sourceware.org/ml/systemtap/2007-q1/msg00183.html
http://sourceware.org/ml/systemtap/2007-q1/msg00184.html

Possible solutions:
* Find a better estimate of the cpu freq
* Use a clock that's independent of cpu freq (e.g., a motherboard/chipset timer)
* Get the kernel to provide a lockless gettimeofday
* Others?

-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=3916

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